In systems which employ a pulsed beam of laser radiation, it has often been found desirable to provide a laser beam pulsed at a rate significantly more rapid than the pulse rates available with any single useful laser. To provide the desired rapidly pulsed beam, techniques and apparatus have been developed for combining two or more separately generated laser beams, each pulsing slower than the desired rate, into a composite beam which will provide a pulse whenever there is a pulse available from any of the input beams, thereby providing a beam having the desired pulse rate.
Conversely, it has been desirable to be able to perform the reverse transposition, i.e., commutating a single, rapidly pulsing laser beam into a number of separate beams of slower pulse rates. Techniques have thus been developed for decomposing a periodically pulsed beam into multiple "component" beams, and for the distribution of the plurality of beams so created.
Optical beam combiners as well as beam splitters or distributors of both the rotating and nonrotating types are known in the prior art. Many of such prior art designs utilize refractive optics, however. The optical glass required for the refractive elements of such systems is generally of sufficient size and mass as to impose significant limitations on rotational speeds which may be employed; exceeding such maximum usable speeds will subject the glass elements to forces they are incapable of withstanding. And, even in purely reflective systems, excessive rotational speeds may induce distortion in mirror surfaces as a result of the centrifugal induced by rotation.
Optical efficiency is also important when the laser pulses each have high average power, for both refractive and reflective optics. Non-zero optical losses will result in optical distortion due to thermally induced deviations of both reflective surfaces and transmissive optical elements. Further, such losses give rise to problems regarding the removal of the resulting heat flux through the surface areas of the optical elements.